Understanding pH in a koi pond.

The pH is a measurement of hydrogen ions as acidity and hydroxyl ions as alkalinity in the pond water;  pH 0 – 6.99 is acid; pH 7.0 is regarded as neutral, and pH 7.01 – 14.0 is alkaline. pH (potential of hydrogen) is basically a measurement of how acidic, alkaline, or neutral your water is.  It is measured on a scale of 0-14. A neutral pH of 7 simply means that there are an equal number of hydrogen ions as hydroxyl ions. A pH of 8 means your water is alkaline compared to neutral, and has more hydroxyl ions than hydrogen ions All biological process from fish respiration to decaying solids will reduce pH.

The pH level can have a profound effect on the toxicity of ammonia. Alkaline water, with a pH of over 7.01 in combination with increasing temperature causes more of the ammonia to exist in the free form, which is very poisonous to Koi. If the water is alkaline it will affect the toxicity of ammonia and could be quite serious for the health of your pond fish.

It is also very important to understand that each single digit increase or decrease above or below neutral is ten times more alkaline or acidic than the neutral reading of 7. For every single digit change above or below neutral there is a tenfold difference. Any sudden change in pH of one digit or more is a drastic chemical change and could have devastating effects on your fish.

If the water becomes too acid or alkaline, and swings in one direction or the other, the fish have a means of adding acids or bases to their blood to counteract the changes and equalize their internal pH to that of the water. However, they cannot do this very quickly, and they cannot easily counteract a change in the pH of the water of more than three tenths. If the water becomes too acid or too alkaline too quickly, or if the pH goes outside that species’ healthy range for too long, the fish are in danger of getting conditions such as Acidosis or Alkalosis. Both of these conditions can be fatal.

What is the ideal pH for Koi and Goldfish?

Koi and goldfish do best in a pH between 7.0 and 8.6 and most often perish at a level below 6.0.  A relatively stable pH of pond water is vital to our pet fish. Fish need to maintain a very similar pH level in their blood to stay healthy. For Koi to be healthy, they need a pH in the range of 7.0-8.6, and more importantly they need the pH to remain stable somewhere within in that range. Internally, fish are capable of counteracting pH swings, but only to a degree of a three tenths change per day. Ideally, no change should occur.

What are the impacts of high pH on koi?

Pond water conditions with pH of 8.5 or higher may result in a condition within the fish called Alkalosis. Symptoms include excess slime production, isolation, gasping at the pond surface, blood streaked fins, resting on the bottom, and finally death.  Alkalosis is hard to reverse once the symptoms begin.

What are the impacts of low pH on koi?

Low pH levels create a condition called Acidosis in pond fish. The symptoms of Acidosis are similar to those of Alkalosis; a lack of appetite, production of excess slime, isolation and resting on the pond bottom and finally blood streaked fins and death. However, Acidosis is rapidly corrected when the pH level is raised to a suitable range.

How do I check the pH of my koi pond?

The proper way to check pH, is to take two readings with a suitable pH test kit. One should be taken in the early morning and the other should be taken in the late evening on the same day and preferably the same weather conditions. In doing so, you should not have more than a .3 (three tenths) difference between the two readings.

How do I raise the pH of my koi pond?

If your pond experiences a pH crash, meaning the pH dives below 6.5 you can use baking soda at a rate of 1 teaspoon for every 5-10 gallons of pond water. Best practice is to collect some pond water in a bucket and dissolve the recommended amount of baking soda for your pond in the bucket. Then pour the entire contents directly into the pond water. Be sure to rinse out any baking soda that remains on the bottom of the bucket. Alternatively, you can drop the baking soda directly into the pond where it will dissolve naturally.